52393T Mercruiser DRIVER HEAD TOOL

Fuel System
FUEL SYSTEM SCHEMATIC
1. Bleed valve. 2. Fuel injection pump. 3. Bleed manifold. 4. Fuel manifold. 5. Precombustion chamber. 6. Fuel transfer pump bypass valve. 7. Priming pump. 8. Bleed valve. 9. Fuel tank. 10. Primary fuel filter. 11. Fuel transfer pump. 12. Fuel filters.Fuel is drawn from the fuel tank through the primary fuel filter (10) by the transfer pump (11). This pump is mounted on the fuel filter housing and is driven by a shaft connected to the fuel injection pump camshaft.A bypass valve (6) at the inlet side of the fuel filter assures adequate pressure for the fuel system and allows excess fuel to be bypassed back to the fuel tank (9) through a return line.A fuel priming pump (7) is used to fill the filter case, pressurize the fuel and assure that the system is free of air prior to starting the engine. A system of check valves allows fuel to be pumped past the fuel transfer pump when the priming pump is in use. As the filter (12) and fuel injection pump (2) passages are being filled with fuel from the priming pump, bleed valve (8) on the filter housing can be opened to allow air to escape. The bleed valve (1) on the fuel manifold can be used to allow any entrained air to escape from the individual fuel pumps and eliminate the need for loosening fuel line connections at the individual fuel pumps.Individual fuel injection lines carry fuel from the pumps to each cylinder. One section of line connects between the fuel injection pump and an adapter on the inward portion of the camshaft housing. Another section of line on the inside of the camshaft housing connects between the adapter and the top of the precombustion chamber.The fuel pump camshaft is driven by gears located inside a cover at the rear of the engine. An adjustable drive gear at the rear of the engine vee, drives a speed sensing, variable timing unit which in turn is coupled to the fuel pump camshaft through a sliding spline. This variable timing unit automatically provides retarded timing for easier starting and smooth low rpm operation. It will also advance timing as engine rpm increases to provide optimum engine operating efficiency.Fuel Injection Pump
Fuel enters the fuel injection pump housing through passage (6) and enters the fuel injection pump body through the inlet port (2). The injection pump plungers (5) and the lifters (11) are lifted by the cam lobes (12) on the camshaft and always make a full stroke. The lifters are held against the cam lobes by the springs (3). Each pump measures the amount of fuel to be injected into its respective cylinder and forces it out the fuel injection nozzle.
FUEL INJECTION PUMP
1. Check valve. 2. Inlet port. 3. Spring. 4. Lubrication passage (fuel). 5. Pump plunger. 6. Fuel passage. 7. Bleed passage. 8. Fuel rack. 9. Lubrication passage (oil). 10. Gear segment. 11. Pump Lifter. 12. Camshaft lobe.The amount of fuel pumped each stroke is varied by turning the plunger in the barrel. The plunger is turned by the governor action through the fuel rack (8) which turns the gear segment (10) on the bottom of the pump plunger. Passage (4) provides fuel to lubricate the pump plunger and passage (7) allows air to be bled from the system through the valve on top of the fuel filter case.Fuel Injection Valve
Fuel, under high pressure from the injection pumps, is transferred through the injection lines to the injection valves. As high pressure fuel enters the nozzle assembly, the check valve within the nozzle opens and permits the fuel to enter the precombustion chamber. The injection valve provides the proper spray pattern.
FUEL INJECTION VALVE CROSS SECTION
1. Fuel line assembly. 2. Seal. 3. Body. 4. Nut. 5. Seal. 6. Nozzle assembly. 7. Glow plug. 8. Precombustion chamber.Speed Sensing, Variable Timing Unit
The variable timing unit, couples the fuel injection pump camshaft to the engine rear timing gears. The variable timing unit advances the timing as engine rpm increases.On earlier engines the timing advances from 11° BTC at low idle to 19° BTC at high idle. On later engines the timing advances from 8° BTC at low idle to 19° BTC at high idle.
LOW RPM POSITION
1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.During engine low rpm operation, the flyweight (8) force is not sufficient to overcome the force of control valve spring (3) and move control valve (7) to the closed position. Oil merely flows through the power piston cavity (2).As the engine rpm increases, flyweights (8) overcome the force of control valve spring (3) and move control valve (7) to the closed position, blocking the oil drain port (6). Pressurized oil, trapped in power piston cavity (2), overcomes the force of spring (4) and moves power piston (1) outward. This causes the fuel injection pump camshaft to index slightly ahead of the shaft portion (9) of the variable timing unit. Any outward movement of the power piston increases the force on the control valve spring. This tends to reopen the control valve, letting oil escape from the power piston cavity. As oil begins flowing from the cavity again, return spring (4) moves the power piston inward.
HIGH RPM POSITION
1. Power piston. 2. Power piston cavity. 3. Control valve spring. 4. Power piston return spring. 5. Oil inlet passage. 6. Drain port. 7. Control valve. 8. Flyweights. 9. Shaft assembly.At any given rpm, a balance is reached between the flyweight force and the control valve spring force. The resultant position of control valve (7) will tend to maintain proper pressure behind the power piston. The greater the rpm, the smaller the drain port opening, and the further outward the power piston is forced.As the power piston is moved outward, the angular relationship of the ends of the drive unit change. As the power piston moves